Voice Monitoring System for Airline Pilots.Chaos theory tells pilots when to take a break.AIRLINE pilots and air traffic controllers who are too tired towork safely could soon be identified automatically, thanks toa Japanese monitoring system that analyses voice patternsfor signs of fatigue. "Our system is able to detect tiredness in test subjects 10 to 20 minutes before the subjects themselves notice it," says Kakuichi Shiomi, chief researcher at the Electronic Navigation Research Institute near Tokyo, which developed the system. Human error currently accounts for around 80 per cent of all air accidentsworldwide. "Crew fatigue is a very real problem, especially on long-haulflights crossing many time zones," says Shiomi.Called a fatigue and drowsiness predictor, the system uses the mathematicsof chaos theory to compare changes in the voices of wide-awake, alertpeople with those of fatigued people. The change is known to be relatedto a drop in blood pressure when people are tired-but it is very subtle.So Shiomi's team at ENRI, a division of the Japanese Ministry of Transport,had to come up with a way of analysing speech that brings these smallchanges into sharp relief.The system takes advantage of the fact that many biological signals,including heartbeat and blood pressure-have a fractal structure.Like a coastline or a lightning flash, the pattern of the signal is equallyjagged no matter how closely you zoom in on it. But with voice signalsthere's one important difference: the fractal structure changes whenthe speaker is fatigued.The changes are hard to spot by simply watching the voice waveform,so the ENRI team wrote software that converts a voice signal's fractalstructure into a graphical pattern that magnifies subtle, small changes.Alert voice pattern has a well-ordered trace.Drowsy voice pattern is chaotic and spiky.To test their system, the researchers processed recordings of subjectsas they concentrated on reading or doing maths. When wide awakeand alert, their voice fractal graphics are well defined (see Diagram).But after 20 to 30 minutes of reading, they become noticeably morejagged. In a cockpit or air traffic control centre, an image processorcould recognise the fatigue pattern and raise the alarm when staff arebecoming fatigued, signalling that it's time for a more alert colleagueto take over.Tests of the fatigue predictor are now planned on real pilots and air trafficcontrollers. If these are successful, Shiomi envisages using the systemon other transport systems, such as oil tankers, where the verbalcommands of drivers and pilots can be monitored._______________________________________________________From an article in the New Scientistby Peter Hadfield and Paul MarksWeb: www.newscientist.comDecember 2000